This project is an investigation of prostaglandin metabolism in rheumatoid synovial cells in tissue culture. The products of polyunsaturated fatty acid metabolism are being characterized and their regulation by a low molecular weight protein factor produced by rheumatoid synovial tissue in explant cultures will be examined. The influence of changes in fatty acid composition in cells in tissue culture on prostaglandin metabolism will be studied. Measurements of prostaglandin concentrations in synovial fluids from patients with rheumatic diseases are planned.